This invention relates to an apparatus for producing a fiber lap from fiber tufts and is of the type which has a substantially vertical chute (feed chute) of rectangular cross section. The chute has two facing wide vertical walls and two facing narrow vertical walls as well as a width dimension which is the horizontal distance between the two narrow vertical walls. The upper end of the chute is provided with a fiber tuft supplying device, while its lower end accommodates a device for withdrawing the fiber tufts and discharging them as a fiber lap. One of the wide walls of the chute is air pervious and has, along the chute width, a plurality of side-by-side arranged elements for varying the air flow in the chute at those locations.
As disclosed in German Offenlegungsschrift (application published without examination) 34 13 595, a series of parallelepiped-shaped bodies of identical width are arranged in an opening which is provided in a chute wall facing the air pervious chute wall and which extends along the width of the feed chute. Each body is horizontally shiftable by an electromagnet so that the cross section of the feed chute is variable at those locations, whereby the air flow may be altered. The electromagnets are coupled to a control device. The opposite end regions (edge zones) of the chute wall, as viewed along its width, are covered by a relatively wide body. A carding machine is arranged immediately downstream of the feed chute for receiving the fiber lap therefrom. As a rule, the fiber lap has a width of 1 m.
Particularly in roller card units which have a width of 2.50 m or more, a spreading of the fibers in the edge zones occurs. At the output of the roller card unit such a spread leads to a reduction of the desired weight at the edge regions of the web (edge regions of the delivered fiber lap) and thus necessarily leads to a reduction of the useful output width. Further, the excessively light web edges lead to a more pronounced soiling of the machine at the roll ends which requires a more frequent servicing (maintenance work) of the machine.